Orthopaedic supports are used to provide structural support and/or limit movement of a portion of a patient's anatomy. Hardenable splints and casts are commonly formed by wrapping or otherwise positioning layers of a strip or “tape” of hardenable material about the afflicted area and allowing the material to harden in place. Gauze coated with calcined gypsum has been used for many years, but more modern hardenable supports are formed with other fabrics, e.g., knitted fiberglass, and employ hardenable organic resins instead of calcined gypsum. For example, U.S. Pat. No. 4,996,979, granted Mar. 5, 1991, and U.S. Pat. No. 4,683,877, granted Aug. 4, 1987 disclose water-hardenable organic resins used in this context. Other hardenable resins used in this field include epoxies and UV-curable materials.
When using such tapes in forming orthopaedic supports, multiple layers of the tape are wrapped about or positioned on the limb or other affected part of the patient's anatomy. In applying the tape to form a cast, for example, care must be taken to firmly engage the layers during the exotherm portion of the setting period to ensure unitary bonding of the entire layered cast or assembly. This step requires care and expertise to ensure that the layers are properly bonded without causing pain or discomfort to the patient, e.g., when forming a cast around a broken limb. Applying fiberglass tape to form a water-hardenable core of a splint or support requires considerable skill and practice to form splints or supports of varying thickness which may be required or which may be desirable for certain applications. Thus, for example, when a cast is to be provided for a foot and lower leg, it may be desirable to have greater thickness in the lower portion of the cast, and a lesser thickness in the vicinity of the shin or the calf of the user. Applying layers of fiberglass cloth requires considerable experience to form a varying thickness layered cast or support which will have proper inter-layer bonding and strength.
Not all hardenable orthopaedic supports are formed by winding an elongate strip of tape around the limb or other anatomical structure. For example, U.S. Pat. No. 6,186,966, granted 13 Feb. 2001 and entitled “Hardenable Orthopaedic Support With Improved Configuration”, suggests a support which, in one configuration, may be pre-shaped to be reliably placed on an anatomical structure, e.g., a palm, wrist and forearm. Certain embodiments include a pair of spaced interwoven layers formed of high-strength materials with an open matrix of filaments or threads interconnecting the layers. The support is flexible and can conform to the intended anatomical structure without forming wrinkles, which lend the product an unsightly appearance and can lead to patient discomfort. This approach also avoids the necessity to wrap plural layers of tape, contour the tape to appropriately fit the limb, and compress the layers together to avoid delamination.
Another problem encountered in this field is the fraying of the edges of material when fabric, such as fiberglass fabric, is cut. When the hardenable resin cures, the frayed edges may harden and may cause patient discomfort or abrade adjacent soft tissue. This difficulty often plagues orthopaedic supports, including pre-shaped hardenable supports. Typically, the material which carries the resin is coated in a continuous process, e.g., by spraying or dipping the material in a bath of the resin and squeezing out some of the excess resin between a pair of rollers. Many commercially available hardenable resins, e.g., urethane resins, are viscous, tacky fluids which may stick to a die or other cutting equipment, making it very difficult to cut desired shapes. As a consequence, most commercially successful hardenable orthopaedic supports to date are sold in the form of continuous tape or rectangular swatches of a predetermined size, which must then be arranged on the patient's limb.
Some hardenable orthopaedic supports employ an inner structure which carries the hardenable resin and one or more external layers. For example, one of the splint structures suggested in U.S. Pat. No. 6,186,966, noted above, includes a water-pervious outer layer and an inner layer adapted to keep the patient's skin dry. Water-hardenable orthopaedic supports are often stored and shipped in sealed, water-impervious packages, e.g., a plastic blister pack. The resin is in contact with the our layers during storage and shipment and, over time, resin can migrate through one or both of the outer layers. When this product is removed from the package, wetted (if necessary) and applied to the patient, the resin on the outside of the product can harden on the physician's or technician's hands and can harden on the patient's skin. This can also lead to an irregular, mottled surface, making the support less attractive and lending a less professional appearance.